The present invention relates, in general, to rather commonly used multi-mode friction type brake systems which are disposed, for example, on each truck portion of a subway type transit vehicle and/or a light rail type transit vehicle. More specifically, this invention relates to wheel slip control safety functions, and safety timers which can interrupt a wheel slip control operation to protect magnet valves from excessive wear.
It will be appreciated that, in railway and mass and/or rapid transit operations, it is common practice in a complex logic wheel slip and brake control system f or an operator to manually actuate the wheel slip inhibit and, additionally, to have a safety timer and magnet valve state feedback to establish safeguards and to control the operational event recorder. During a long haul, where the train makes infrequent stops, the prior art may timeout inadvertently and the truck would be without wheel slip correction for a long period, such as, until it makes its next stop.
It will also be appreciated by people skilled in the art that presently used safety timers depend on vehicle axle speeds, brake indications, and/or trainline Signal to initiate a safety timer reset. These all utilize a network to communicate with external interfaces and this communication is performed through the use of software. Using a network and its inherent use of software for a safety circuit is problematic due, for example, to component reliability and electrical transmission problems of the network.
In one aspect the present invention provides a time reset safety timer circuit for use on a rail vehicle comprising a plurality of trucks. The time reset safety timer circuit includes a truck timeout timer connected to a truck timer circuit for receiving a timed out signal from the truck timer circuit. Upon receiving a start timer signal the truck timer circuit waits a first predetermined time and then sends a timed out signal to the truck timeout timer. The truck timeout timer, upon receipt of the timed out signal from the truck timer circuit, waits a second predetermined time and then resets itself and the truck timer circuit.
The truck timer circuit also connects to a truck power feed interface, and a truck wheel slip detection circuit. The truck timer circuit energizes the truck power feed interface when the truck timer circuit is not in a timed out state. It also de-energizes the truck power feed interface when the truck timer circuit is in a timed out state. That is to say the truck power feed interface can be used for interrupting a power feed from a truck magnet valve driver circuit to a truck wheel slip magnet valve. A truck wheel slip detection circuit can be used for detecting when the truck wheel slip magnet valve has been energized and for sending an energization indication signal to the truck timer circuit. It can also be used for detecting when the truck wheel slip magnet valve has been de-energized, and for sending a de-energization indication signal to the truck timer circuit. The truck wheel slip magnet valve can be used for changing the truck brake cylinder pressure when energized from the truck magnet valve driver circuit.
Another aspect of the present invention provides a safety timer, driver, and magnet valve module for use on a rail vehicle comprising a plurality of trucks. Wherein the safety timer, driver, and magnet valve module includes a truck timeout timer connected to the truck timer circuit for receiving timed out signals from the truck timer circuit. Upon receiving a timed out signal from the truck timer circuit the truck timeout timer waits a predetermined time and then sends a reset signal to itself and the truck timer circuit.
The truck timer circuit also connects to a truck power feed interface, and a truck wheel slip detection circuit. The truck timer circuit energizes a truck power feed interface when the truck timer circuit is not timed out. It also de-energizes the truck power feed interface when the truck timer circuit is in a timed out state. The truck power feed interface can be used for interrupting a power feed from a truck magnet valve driver circuit to a truck wheel slip magnet valve driver. The truck wheel slip detection circuit can be used for detecting that the truck wheel slip magnet valve has been energized and for sending an energization indication signal to the truck timer circuit. It can also be used for detecting that a truck wheel slip magnet valve has been de-energized and for sending a de-energization indication signal to the truck timer circuit.
A further aspect of the present invention is to provide a time reset safety timing circuit comprising a safety timer which interrupts a wheel slip control operation after a first predetermined time after the wheel slip control operation begins, and to provide a timeout timer which resets the safety timer circuit after a second predetermined time after the safety timer interrupts the wheel slip control operation.
Still another aspect of the present invention is to provide a method for interrupting and to stop interrupting a wheel slip control operation. This method includes waiting a first predetermined time period after an onset of the wheel slip control operation, and interrupting the wheel slip control operation after the first predetermined time period if the wheel slip control operation is continuous during the first predetermined time period. Waiting for a second predetermined time period after the wheel slip control operation has been interrupted and removing the interruption of the wheel slip control operation, and, if the wheel slip control operation is running when the interruption has been removed, waiting a first predetermined time period and repeating the interruption of the wheel slip control operation, waiting a second predetermined time, and removing the interruption of the wheel slip control operation.
It is, therefore, one of the primary objects of the present invention to provide a time Preset safety timer circuit that contains simplified and minimized external interfaces.
It is also an object of the present invention to provide a time reset safety timer circuit that improves reliability through the use of internal information to initiate a safety timer reset.
An additional object of the present invention is to provide a time reset safety timer circuit that allows for easier application of a distributed electronic system.
Another object of the present invention is to provide a time reset safety timer circuit that allows the wheel slip control to be restored without having to stop the train.
Additional objects of the present invention are the benefits for long hauls passenger train services where the trains makes infrequent stops. For this type of service, a prior art safety timer may timeout inadvertently and the truck would be without wheel slip correction for a long time period. Utilizing the present invention, the wheel slip control can be restored without the need to stop the train.